Multnomah county's top law enforcement officers are calling for the state's top attorney to investigate County Chairman Jeff Cogen.

Multnomah County District Attorney Rod Underhill and Multnomah County Sheriff Dan Staton say they're asking Oregon Attorney General Ellen Rosenblum to investigate any potential misuse of county funds by Cogen during his 18-month long affair with county health official Sonia Manhas. They're also asking Rosenblum to decide if there are potential criminal charges that could stem from that spending.

Rosenblum has agreed to undertake the investigation. Attorney General spokesman Jeff Manning says  his office got the request from Underhill and Staton at 3:30 pm today.

The Attorney General's Criminal Justice Division will perform the investigation, which will begin immediately, Manning says.

He can't say how long it will take: "We'll go where the investigation takes us."

The investigation is part of a particularly chaotic day in county government stemming from Cogen's July 16 admission of an affair with Manhas. Manhas, saying she was forced out, signed a letter of resignation today. Cogen, who is the county's top elected official, has pledged not to resign, saying he's a "fighter."

Underhill and Staton's announcement of an outside investigation comes on the heels of the four other county commissioners—Deborah Kafoury, Loretta Smith, Diane McKeel and Judy Shiprackasking for an independent investigation by Rosenblum or a third party yesterday.

Here's a copy of the letter the two sent today: