MARTINEZ -- A bounty of weapons and ammunition in a Bay Point home -- so much that bullets and guns were placed on cabinets and the floor -- were seized during a police raid in May, in what authorities on Thursday called the largest weapons haul in decades.

In all, authorities pulled 56 guns, 30,000 rounds of ammunition and an unspecified amount of methamphetamine for sale from the home on May 9. The raid represents the most successful month for the Contra Costa County Anti-Violence Suppression Effort, formed in August 2011, officials said.

"There's a good chance (we) prevented something from happening," said Pittsburg police Lt. Patrick Wentz, whose department established the task force with the Contra Costa County Sheriff's Office, California Highway Patrol and the state Department of Justice.

The agencies displayed the weapons during a joint news conference in Martinez on Thursday.

Five people were arrested in the Bay Point case. Police did not release their names nor did they give an address for the home Thursday, saying the cases are active investigations. Authorities said a home in the residential Shore Acres neighborhood had guns in a safe but others in plain sight and not secured. Only two of the guns -- a SKS assault rifle and an AR-15 assault rifle -- would be illegal for non-felons to possess. The five suspects were arrested because of their criminal history and gang ties, police said.

Lt. Ted Anderson, of the Contra Costa Sheriff's Office, said the seizure is the largest he has seen in his 27 years in local law enforcement. It was the largest gun recovery operation by CASE.

In all of May, investigators handled seven cases, made 14 arrests and took 81 guns off the street, officials said. One person was arrested May 15 in Antioch for being in possession of an assault rifle and illegal possession of a firearm and ammunition. In that search, two M-4 assault rifles, three rifles, two pistols and six high-capacity magazines were seized.

Since its inception, CASE has made 142 arrests and seized a total of 447 guns.

David DeBolt covers breaking news. Contact him in Richmond at 510-262-2728. Follow him at Twitter.com/daviddebolt.