A federal judge ordered a probe Thursday into how Oakland police investigate officer-involved shootings and threatened the department with sanctions if misconduct is uncovered.

U.S. District Judge Thelton Henderson also ordered Oakland to provide by June 8 additional information showing how it will complete already past-due internal affairs investigations stemming from last year's Occupy protests. He threatened to levy daily fines against the city if it again misses deadlines to complete the investigations.

Henderson oversees police reforms ordered as part of the 2003 settlement of the Riders police misconduct case. On Thursday, he again questioned whether police would ever be able to fully implement the reforms and warned that he was still considering proceedings to place the department under federal control.

Robert Warshaw, the federal monitor overseeing Oakland police, raised concerns to Henderson about how the department investigates officer-involved shootings, including the proceedings of the Executive Force Review Board and subsequent deliberations by the police chief and his supervisors.

"This is of utmost concern, as uses of force and the manner in which they are investigated are among the most serious issues in (the Riders) case," Henderson wrote, "and officer-involved shootings, many of which result in death, are the most grave possible uses of force."

Warshaw, a former U.S. deputy drug czar, will report his findings in his next report to Henderson, scheduled to be completed this summer.

Jim Chanin, an attorney who represented the plaintiffs in the Riders case, said he hoped the probe would help Oakland reduce its "high rate" of officer-involved shootings. "It's very important that these investigations have credibility with the public," he said.

There have been three officer-involved shootings this year in Oakland. The only fatal shooting claimed the life of Alan Blueford, who police said had pointed a gun at the officer who shot him.

Oakland recorded five fatal officer-involved shootings last year.

With regard to Occupy, the city last month satisfied Henderson's order to produce a plan for completing past-due internal affairs investigations into complaints stemming from the Oct. 25 Occupy Oakland protests.

Henderson on Thursday ordered the city to provide by June 8 additional information including the deadlines for completing key tasks and the names of people responsible for making sure the deadlines are met.

Oakland spokeswoman Karen Boyd said in an email that "The City will comply with the court order and the timelines it sets forth as the court acknowledges we did with the last order."

Henderson also ordered Warshaw to review a city-commissioned study on police handling of Oct. 25 Occupy protests and address its implications. The report, completed by The Frazier Group, had been scheduled to be released in May, but Boyd recently said the city expects to make it public in early June.

Contact Matthew Artz at 510-208-6435