Mexican lawmen stalking drug traffickers mistakenly shot and killed a news anchorwoman, her mother-in-law and a family friend Saturday, authorities said.

Police officers mistook the journalist's car for one spotted near a clandestine airstrip where a plane believed to have been carrying Colombian cocaine had crashed, the official government news agency Notimex reported.Notimex said federal Attorney General Sergio Garcia Ramirez ordered an investigation and the detention of the four police officers involved in the shootings.

XHIJ-TV said its anchorwoman, Linda Bejarano, 28, was killed along with Lucresia Martinez de Gomez, 58, and Carlos Alfonso Garcia, 25.

Bejarano's husband, Manuel Gomez, said he was in the car with the other three when they were shot about 3:30 a.m. near downtown Juarez, but he was uninjured.

Gomez, a co-anchor at the station, told reporters later Saturday that the four were driving near downtown when a car carrying four men tried to pull them over. He said the men identified themselves as Federal Judicial Police officers, but that he didn't stop because he was afraid they would rob him.

He said he was carrying about $12,000 in cash raised by the TV station at a circus.

When Gomez didn't stop, the men started shooting the car with machine guns. About 40 to 45 bullet holes were found in the car, officials said.

Gomez said he was taken in for questioning and then released.

State Judicial Police Commander Ramon Olivas said a car similar in description was found later abandoned with 40 kilograms of cocaine.

"The Judicial Police cowardly killed my wife and my mother," Gomez said, his voice shaking. "I hope the police don't hide and protect these men."

Notimex identified the four as Joaquin Garcia Mendez, a federal judicial police officer, and city police officers Santos Robles Pena, Roberto Gomez Jilguero and Noel Librado Zavala.

Federal Judicial Police officials told the TV station in this border city across from El Paso, Texas, that the gunmen were "madrinas" - uncommissioned officers who often carry guns and act as surveillance agents.

XHIJ spokesman Gustavo Aguirre said police told him the officers were trying to track a similar car supposedly laden with 80 kilograms of cocaine when the shootings occurred.

"They said it was a mistake," Aguirre said. "That's all they say. They thought that they (the victims) were narcotics traffickers because the car was the same type they were looking for."