Two Los Angeles Police Department officers are under investigation for allegedly preying on women over a period of five years, luring them into an unmarked car and forcing them to perform sex acts, according to court records.

Detectives from the LAPD's internal affairs unit suspect that Officers Luis Valenzuela and James Nichols targeted at least four women whom they had arrested previously or who worked for them as informants, according to a search warrant reviewed by The Times.

The pair repeatedly used the threat of jail to get women into their car and drove them to secluded areas where one of the officers demanded sex while the other kept watch, the warrant alleges.

Valenzuela and Nichols worked together until recently as narcotics officers in the Hollywood Division. Investigators have identified four women who encountered the pair and made similar independent accusations against them.

The warrant cites sexually explicit text messages that one alleged victim claims she exchanged with the officers after their encounters. Last month, investigators obtained the woman's cellphone and computers in hopes of finding the messages the officers are alleged to have written. The department has yet to examine the electronic devices, a police official said.

Investigators had planned to confront the officers in a surprise operation early next week, but were forced to accelerate those plans Thursday, when one of the women unexpectedly filed a lawsuit against the officers. Fearing that Valenzuela and Nichols might destroy evidence, investigators rushed to sequester the officers and seize their computers and phones, police confirmed.

LAPD Chief Charlie Beck emphasized Thursday that the investigation was ongoing, but added he was "saddened by the allegations. If they are true, it would be horrific," he said.

Valenzuela, a 15-year department veteran, and Nichols, a 12-year veteran, were expected to be assigned to their homes pending the outcome of the probe, the head of the internal affairs group said. The officers could not be reached for comment.

The first woman to accuse Valenzuela and Nichols came forward in January 2010, when she told a supervisor in their narcotics unit that the officers had stopped her more than a year earlier, according to the warrant. The woman, who worked as a confidential informant for the narcotics unit and knew the men, said they were dressed in plain clothes and driving a Volkswagen Jetta. Valenzuela threatened to take the woman to jail if she refused to get in the car, then got into the back seat with her and exposed himself, telling the woman to touch him, the warrant said.

An investigation into the woman's claim went nowhere when the detective assigned to the case was unable to locate her, according to the warrant.

A year later, however, another woman demanded to speak to a supervisor after being arrested and taken to the LAPD's Hollywood station. Sometime in late 2009, according to the warrant, two officers driving a Jetta pulled up alongside her as she was walking her dog in Hollywood. The officers, whom she recognized as the same cops who had arrested her in a previous encounter, ordered her into the car, the woman recounted. It is not known why she was arrested.

Believing that the officers were investigating a case, the woman said she felt compelled to comply. Valenzuela then got into the back seat with the woman and handed her dog to Nichols, who drove the car a short distance to a more secluded area. "Why don't you cut out that tough girl crap," the woman recounted Valenzuela saying as he "unzipped his pants and forced [her] head down toward his lap and physically held her head down" as he forced her to perform oral sex on him, according to police records contained in the warrant.

The woman said she didn't report the incident immediately because she felt humiliated, thought no one would believe her and feared for her safety. Police noted that the woman displayed erratic behavior while recounting the events. Later, she made violent threats while in custody and was transported to a hospital.

Based on this allegation, the department reopened the investigation into the pair. The investigator assigned to the case interviewed this second accuser and managed, as well, to find the first woman who had come forward the year before. She, too, gave a statement, saying she had refused Valenzuela's commands to fondle him.

For reasons not explained in the warrant, the department's investigation made little progress for the next 18 months. During this time, police records show, the officers were transferred, with Valenzuela being reassigned to the Olympic Division and Nichols to the Northeast Division. (Nichols was involved in the high-profile arrest last year of Brian C. Mulligan, an executive at Deutsche Bank, who alleged he was the victim of excessive force. Police contend that Mulligan, while deranged on drugs, charged at Nichols and suffered injuries while Nichols and his partner took him into custody).

Cmdr. Rick Webb, who heads the LAPD's internal affairs group, declined to comment on the specifics of the probe, but said such cases are often difficult to complete.

The case picked up steam again in July 2012, when a man left a phone message for the vice unit at the Northeast station, saying he was a member of the Echo Park neighborhood watch and had been told by a prostitute that patrol officers in the area were picking up prostitutes and letting them go in exchange for oral sex, the warrant said.

Two more months passed before a third internal affairs officer was assigned to look into the Echo Park claim. The investigator was aware of the earlier allegations against Valenzuela and Nichols and "thought the circumstances and location were very similar."

It is not clear how, but the investigator identified another two women who reported encounters in which Nichols and Valenzuela had sought sexual favors in exchange for leniency.

One said Nichols had detained her in July 2011, handcuffed her and driven her to a quiet location. Removing the restraints, Nichols exposed himself and said, "You don't want to go to jail today, do you?" the woman recalled. Fearing she would be arrested, the woman performed oral sex on Nichols, who then released her, she said. She said Nichols had done the same thing to her six years earlier.

The other woman discovered by the internal affairs investigator alleged that she became a confidential informant for Valenzuela and Nichols after she was arrested, according to the warrant. Valenzuela, she said, told her that having sex with him would help her avoid jail, according to the warrant. She alleged that she had sex with the officer twice, once when he was off duty at her apartment in Los Angeles, and the second time in the back seat of an undercover police car while he was on duty. She said she was afraid he would send her back to jail if she refused.

She said Nichols contacted her in January 2011 and told her he would cancel her obligation to inform for him if she would have sex with him.

The woman filed a lawsuit against the city on Wednesday, alleging that the officers forced her to have sex with them several times in exchange for keeping her out of jail. The Times in general does not name the victims of alleged sex crimes.

That lawsuit was first reported by City News Service. Despite the officers' promises, the woman was sentenced to jail in April 2011 and remains there, the lawsuit alleged. A district attorney's spokeswoman said the woman is serving more than seven years in jail for possession of cocaine with intent to sell and identity theft.