(CNN) -- More than 100 police officers and others were searching Friday in a southeastern Louisiana parish for a murder suspect who escaped from jail with three other inmates, a law enforcement official said.
Timothy Murray, 29, who is charged with murder, remains at large, authorities in Louisiana say.
Searchers are still focusing inside St. Tammany Parish, on the northern shore of Lake Pontchartrain, 30 miles north of New Orleans, said Capt. George Bonnett of the St. Tammany Parish Sheriff's Office.
At large is Timothy Murray, 29, who is charged with murder, Bonnett said. Authorities believe Murray may have been injured during the escape, but Bonnett wouldn't elaborate.
The inmates escaped about 9 p.m. Thursday from the St. Tammany Parish Jail in Covington, Bonnett said. As many as 250 sheriff's deputies, Covington police officers, Louisiana State police and corrections officials were involved in the search overnight, using dogs, two helicopters and thermal-imaging equipment loaned from Livingston Parish, Bonnett said.
The other three men were found about 1:30 a.m. Friday in a wooded area about a mile from the jail, he said.
Three of the inmates were awaiting trial; one already had been convicted, Bonnett said.
The captured inmates were Gary Slaydon, 27; Eric Buras, 30, and Jason Gainey, 27. Slaydon is charged with attempted murder. Buras is a murder suspect and Gainey has been convicted of murder, Bonnett said.
He said the escape was not discovered until a resident and Covington police reported seeing what appeared to be inmates in jail uniforms walking down a street.
About the time those calls came in, jailers were doing a routine head count and found the four men missing, Bonnett said.
He said the means of escape was under investigation, but it has been determined that their escape wasn't due to human error.
He repeated what St. Tammany Parish Sheriff Jack Strain said early Friday: "Four inmates were able to defeat the structure of the maximum security area of our jail."
Deputies have canvassed neighborhoods, going door to door to warn residents that an inmate is still at large.