Johnny Sanchez, 21, remains jailed without bail on five counts of murder. Prosecutors haven't decided whether to seek the death penalty.
They allege Sanchez set the fire Monday after having a dispute with other people squatting at a former acupuncture clinic in the Westlake area near downtown.
Three men and two women died in the fire, which collapsed the roof of the two-story building and left the bodies buried in debris.
Sanchez, a Honduran citizen, was arrested in 2012 for illegally entering California, but he was released a week later after agents determined he had no criminal history or previous immigration violations, the Los Angeles Times reported (http://lat.ms/1V525Uy).
He was ordered to report regularly to immigration authorities, but for unknown reasons deportation proceedings never began, Virginia Kice, spokeswoman for U.S. Immigration and Customs Enforcement, told the Times.
Sanchez stopped reporting in 2014, but no search was made for him, and no request was made for law enforcement agencies to hold him. Such requests generally only happen when the person has a criminal history or has repeatedly tried to enter the country illegally, Kice said.
Sanchez was arrested on suspicion of domestic abuse in January and for drug possession in May and on June 8, but he was quickly released.
County coroner's officials have identified two of the fire victims as Jerry Dean Clemons, 59, and Mary Ann Davis, 44, both of Iowa. They were from the town of Ottumwa and arrived in Los Angeles days before the fire to join Davis' son, the Times reported, citing a relative....
Neighbors said the vacant building had become a hangout for homeless people and drug users in the past two or three months. Trespassers cut their way through a metal garage door off an alleyway.
Two or three small fires also were reported in the alleyway in recent weeks."
Image caption: "Los Angeles Fire Department arson investigators examine the burned-out ruins of an abandoned office building in the Westlake district just west of downtown Los Angeles Tuesday, June 14, 2016. Two men and two women were found Tuesday after a search using cadaver dogs, bringing the death toll to five. One person was found dead when the building burned Monday evening, June 13. Authorities believe the fire was intentionally set. (AP Photo/Richard Vogel)"