(CNN) One of the three inmates who escaped from a California jail last week has turned himself in, Orange County Sheriff Sandra Hutchens told reporters in Santa Ana.

Bac Tien Duong, 43, was taken into custody in Santa Ana on Friday morning.

Hutchens said Duong approached a citizen on the street just before noon and said he wanted to turn himself in.

Another man told reporters that Duong wanted to be at a place where he could be detained safely. How Duong got to the shop was a mystery, the man said.

Duong was the chief suspect in the theft of a white GMC van that was stolen on Saturday, one day after he escaped from a maximum security jail with Hossein Nayeri, 37, and Jonathan Tieu, 20.

Authorities are still looking for the van and the other two escapees.

Police believe the men are in the San Jose area, a 6½ hour drive north.

At an evening news conference, Orange County Sheriff Lt. Jeff Hallock said Duong was with the other men there on Thursday but decided to return to Santa Ana on his own and surrender. Nayeri and Tieu might be headed to Fresno, where Nayeri has some acquaintances.

The spokesman told reporters that the van has been altered; the windows have been tinted and some decals have been removed. It also has a temporary paper license plate.

The remaining fugitives are wearing civilian clothes.

Duong has been cooperative during interrogations, Hallock said.

The fugitives likely escaped after a 5 a.m. headcount January 22, but it wasn't until more than 15 hours later that authorities discovered the sophisticated escape.

The inmates used tools to cut through security bars in a plumbing tunnel and into air vents. They also apparently used sheets braided into ropes to rappel down four to five stories -- about 50 feet -- from the roof of the jail.

Nooshafarin Ravaghi, 44, who taught English-as-a-second-language at the jail, was arrested Thursday in connection with the escape.

Hallock said earlier Friday that investigators knew of handwritten correspondence between Ravaghi and Nayeri.

He wouldn't go into the content of the letters, or say who wrote to whom, or how investigators learned of the letters.

A law enforcement official close to the investigation told CNN's Pamela Brown that some of the writings appeared flirtatious.

Hallock told reporters the letters were personal.

When asked why Nayeri was taking an ESL class when he already spoke English well, Hallock said investigators are looking into the situation and also examining if the connection he and Navaghi have to Iran played a part.

Navaghi will be arraigned Monday. A bail hearing will be held then, and investigators will recommend bail of $500,000.

She will face a charge of being an accessory to a felony, Hallock said. It is unclear whether Navaghi has an attorney.

She has denied giving the escapees tools, but has admitted giving a Google Earth image, on paper, showing the area around the jail complex, to Nayeri, according to Hallock.

Officials have said Navaghi passed a background check and also attended seminars about fraternizing with inmates.

Authorities have offered a $200,000 reward for information leading to the fugitives' capture, $50,000 of which was designated for each escapee.