SANTA ANA, Calif. (AP) — Unlike similar escapes where dangerous inmates fled into rural areas, the three men who broke out of a Southern California lockup escaped into densely populated suburban communities where they have close ties.

Hundreds of officers are focusing on neighborhoods where the trio charged with violent crimes could be hiding among friends, family or fellow gang members, particularly Orange County's huge Vietnamese population, authorities said Tuesday, the fourth day of the manhunt.

It is just a few miles from the jail where the trio broke out Friday, and two of the inmates, Jonathan Tieu, 20, Bac Duong, 43, have deep ties to the community, which is among the largest in the U.S.

Sheriff's officials put out a call in both English and Vietnamese on Monday for help in finding them. The two "may be embedded" there, said sheriff's Lt. Dave Sawyer, who is leading the investigation.

"We sincerely need input from the community to help us," Sawyer said.

Tieu, Duong and Hossein Nayeri, 37, are considered dangerous and all were awaiting trial for separate violent felonies, authorities said. They have now each been charged with the escape.

Tieu had been held since 2013, accused of murder and attempted murder. Duong faced attempted murder and assault charges in the shooting of a man on his front porch. Nayeri was arrested in 2014 on charges including kidnapping and torture. Authorities said he abducted a marijuana dealer, burned him with a blow torch and cut off his penis because Nayeri thought the man had buried money in the desert.

The men were gone for as long as 16 hours before officials noticed they were missing from the common dorm they share with more than 60 other inmates at Orange County Central Jail. An attack on a guard delayed a Friday night head count by hours.

The trio sawed through a quarter-inch-thick grill on a dormitory wall, got into plumbing tunnels and then sawed through half-inch-thick steel bars as they made their way behind walls to an unguarded area of a roof atop a five-story building. There, they moved aside razor wire and rappelled to the ground using a bed linen.

The sheriff's department has been slow to add more rooftop security cameras at the jail despite a grand jury's recommendations for eight years straight, according to a report Monday in the Orange County Register (http://bit.ly/1OLYVow ). The department has said since 2008 that budget constraints prevented upgrades to the camera systems at the five county jails.

The escape was eerily similar to one last year in New York, where two inmates cut through a portion of a wall hidden under a bunk bed and used piping and tunnels inside the facility to get out. But the search for the pair focused on nearby woods instead of a dense urban population.

A major question for California investigators will be how the men could plan and execute their escape with such precision, said Kevin Tamez, a managing partner for MPM Group, a Philadelphia-based firm that consults on prison security, management and infrastructure.

There is no evidence so far that the trio had help from the inside, but authorities know it's a possibility, Orange County sheriff's Lt. Jeff Hallock said.

It's likely someone slipped them blueprints or told them how the bowels of the jail were laid out, he said.

"If I were whoever's investigating, there are some people who would be on a polygraph, I guarantee you," Tamez said. "They had to have had some inside help."

Motion sensor cameras — available for $55 and often used as baby monitors — can be installed along interior tunnels and pipes to catch inmates, Tamez said. Thorough searches of dorms likely would have discovered tools or damage to the vent grill, he said.

It was the first escape in nearly three decades from the California facility built in 1968. It holds 900 men and is in Santa Ana, about 30 miles southeast of Los Angeles.

Hallock said the jail's general policy is to do walk-throughs every hour to check on inmates. More thorough searches are done randomly, he said, declining to give more details.

It's unclear why the inmates — who are charged with violent felonies — were housed in the common dorm with dozens of others. Assigning them to a large, busy room likely made it easier for them to avoid detection, said Martin Horn, a professor of corrections at John Jay College of Criminal Justice at City University of New York.

Federal authorities are offering $50,000 for information leading to their capture.