Image copyright AP Image caption The inmates, left to right: Jonathan Tieu, Hossein Nayeri and Bac Duong

A manhunt is under way for three "dangerous" inmates who escaped from a maximum security jail in California.

The men, who may be armed, crawled through plumbing tunnels and climbed down the building using bed sheets for ropes.

Authorities are determining whether the men had help from anyone inside or outside the Orange County Men's Jail when they made their escape on Friday.

All three men were set to go on trial separately for violent crimes.

"Each of the escapees should be considered dangerous," said Lt Jeff Hallock of the Orange County Sheriff's Department.

Jonathan Tieu, 20, Bac Duong, 43 and Hossein Nayeri, 37, used tools to cut through the wall of their dormitory.

Clambering through the plumbing system, they made it to the roof and then abseiled to the ground.

Image copyright AP Image caption The inmates abseiled to the ground from the roof

Sixteen hours passed before the jail staff noticed. They suspect the escape was a long time in the planning.

"We're talking about breaching, in some places, significant amounts of steel, rebar and metal," said sheriff's lieutenant Jeff Hallock.

"We're going to take a look at everybody who may have been assigned there. What I can assure you is that the compromises in security have been shored up.''

Image copyright AP Image caption The inmates used tools to cut through various walls

This is the first escape from this jail in 20 years, officials said.

Tieu had been held on murder charges since 2013, Bac Duong was being held on attempted murder charges and Nayeri was being held on kidnapping and torture charges, among others.

There is a $50,000 (£35,100) reward for information leading to their recapture.

"There are people out there that know who these people are, who may have seen them. We're asking for phone calls, whether it's any piece of information you may have,'' Mr Hallock said.

Last summer, New York state inmates Richard Matt and David Sweat used tools that allowed them to break through the walls of their cells to freedom, setting off three weeks of searching.

Matt was later shot and killed by authorities while Sweat was captured.

A prison aide was found to have provided the tools and will serve a prison term.