LOS ANGELES: Los Angeles fire-fighters remained on arson alert early Sunday after the Hollywood district celebrated the New Year under the cloud of a string of deliberately-set fires.

By shortly after midnight (0800 GMT Sunday) the LA Fire Department (LAFD) had been called to at least two carport fires in the Hollywood area, but it was unclear if they were linked to arson attacks of the previous two days.

More than 30 fires were started overnight Thursday and Friday, mostly targeting cars either outside homes on in car ports under buildings, which then caught light, although no serious injuries have so far been reported.

The Los Angeles Fire Department (LAFD) said the threat of more arson attacks added to what is traditionally a busy night anyway, as Angelenos celebrate the new year on a balmy Saturday evening.

"Our crews have been told they are going to be busy tonight, no question about it," said spokesman Brian Humphrey at the start of the New Year's Eve evening.

"We are going into what we call 'augmented dispatch,' where we send extra crews to every call... If things get busy in one part of town, we will move crews in from another."

Federal investigators have been called in to help the LA Police Department (LAPD) and LAFD probe the string of arson attacks, one of the worst arson sprees in city history.

Overnight Thursday and Friday, a total of 17 cars or small trucks were torched in the northern LA district of Los Angeles and the neighboring municipality of West Hollywood.

Then overnight into Saturday another dozen or so vehicles were torched in the San Fernando Valley, just to the north.

In many cases, the fires appeared to have been set within minutes of each other. Los Angeles Deputy Fire Chief Mario Rueda described it as "a night of managing chaos."

Damaged property included a Hollywood Hills home where singer Jim Morrison of The Doors -- whose hits include "Light My Fire" -- once lived, and where he wrote the legendary band's "Love Street."

At least two people are under arrest, according to media reports, including a 22 year-old man charged with starting three fires on Thursday. But they were behind bars overnight Friday and Saturday when new blazes were set.

City and county officials, along with the federal Bureau of Alcohol, Tobacco, Firearms and Explosives (BATF), have posted a reward of $60,000 for information leading to the arrest of those responsible.

LAFD spokeswoman Humphrey said the department was ready for a long night, with or without new arson attacks.

"People forget we will have all the extra and normal traffic that we normally have (on a holiday), like people having babies, and traffic crashes after midnight," he added.