Police have received a number of substantial leads on and reported sightings of a convicted double murderer who broke loose from Texas' death row, the sheriff's office said Friday.

They are continuing to hunt down Charles Victor Thompson (search), 35, and trying to figure out exactly how he escaped from the Harris County Jail (search) late Thursday.

"He is extremely dangerous," said Lt. John Martin of the Harris County sheriff's office in a press conference Friday. "We've received a number of significant leads. We do continue to actively search for him."

Martin wouldn't disclose details of the tips his office was investigating.

Thompson somehow found some civilian clothing, changed out of his orange jumpsuit and used a fake ID badge with a photograph and black strip on the back to break out of prison, according to Martin. The convicted killer was in Houston after being re-sentenced last week to execution.

The successful escape could be blamed 100 percent on human error, according to the sheriff's office, since Thompson had to pass by deputies at three or more different locations.

Martin said Thompson told a deputy he was with the Texas Attorney General's office conducting an investigation at the jail, and the story "was convincing enough that the deputy let him out of the facility," the Houston Chronicle online quoted him as saying. "He may have been taken out of the cell block and put in the attorney booth in the guise of having an attorney visit."

But there were still many puzzles left unsolved in how Thompson managed to get through the system and walk free, according to Martin, who said it wasn't clear how he got out of handcuffs. Police so far had "no idea" whether a door was unlocked or he "defeated" the security system.

"Our suspicions are that he may have kept some legal documents with him when he came back from court," Martin told the news conference. "It does suggest that this was preplanned."

He said the intricacy of the plot also could point to accomplices Thompson may have had in breaking out. Investigators were questioning jail employees.

Police didn't know whether Thompson fled on foot or by car.

Thompson had been expected to be returned to the Texas prison system within 45 days, according to Department of Criminal Justice spokeswoman Michelle Lyons.

He was condemned for the 1998 shooting deaths of his ex-girlfriend, Dennise Hayslip, 39, of Tomball, and her new boyfriend, Darren Keith Cain, 30, of Spring.

The Texas Court of Criminal Appeals (search) later upheld his 1999 conviction, but had ordered a new sentencing hearing.

He was re-sentenced by a jury Oct. 28.

The Associated Press contributed to this report.