By Barbara Liston

ORLANDO, Fla. (Reuters) - The Florida nightclub where the deadliest mass shooting in modern U.S. history occurred last month was broken into just hours after police released the business back to its owners on Wednesday, Orlando police said.

Burglars used a prying tool to remove plywood that had been screwed to an exterior metal door frame at Pulse, a gay dance club, and forced their way inside, a police report said.

The club's owners reported the break-in on Thursday morning, police said. The police report did not say whether anything was stolen or disturbed.

Local law enforcement had been guarding the site since the June 12 attack by shooter Omar Mateen, who killed 49 people and wounded 53 others before he was killed by police after taking hostages during a three-hour standoff.

But the building was transferred back to its owners on Wednesday, police spokeswoman Michelle Guido said in an email, meaning police were no longer responsible for guarding it.

The club's alarm system and interior cameras were not activated at the time of the break-in, police said in their report.

"Since June 12, we have seen the worst and best of human behavior," club owner Barbara Poma said in a statement through a spokeswoman. "We are disappointed that someone felt compelled to violate the privacy of our beloved Pulse nightclub and the sacred place it has now become."

The club will remain closed to the public as owners plan for its future, said Poma, who founded it to honor her brother who died of AIDS and to support the lesbian, gay, bisexual and transgender community.

The massacre took place during a Latin night celebration.

Mateen, 29, a U.S. citizen born in New York to Afghan immigrant parents, claimed allegiance to the leader of the Islamic State militant group in a phone call with authorities during his rampage.

U.S. authorities believe that Mateen, who lived in Fort Pierce, Florida, with his wife and young child, was self-radicalized and acted alone without assistance or orders from abroad.

(Additional reporting and writing by Colleen Jenkins in Winston-Salem, North Carolina; Editing by Tom Brown)