BART must slow trains between south Hayward and Union City stations for six to eight weeks, in the wake of two electrical fires Saturday that caused millions of dollars in damage to power and train control equipment, transit officials said Monday.

Riders still can reach their destinations at the usual time — if they arrive 10 to 15 minutes earlier than normal for trips to or from four stations: Hayward, South Hayward, Union City and Fremont.

Trains will leave those stations 10 minutes earlier than normal to make up for delays caused by trains running on manual control at 25 mph between Union City and South Hayward.

Service elsewhere on BART remains normal and no other train schedules have been changed.

"The simple message is for most parts of the system, everything is normal except for riders going to or from Hayward, South Hayward, Union City and Fremont," said BART spokesman Linton Johnson. "You've got to arrive 10 or 15 minutes earlier at BART if you're going to or from those stations."

The cause of the two electrical fires at a power substation near South Hayward remains under investigation.

The flames destroyed the computerized equipment that controlled trains and electricity to a section of tracks. BART's Hayward train yard was also left powerless.

BART officials acknowledged there were rough spots in the commute Monday caused by passengers being unaware that train connections and schedules had been changed to accommodate the train slowdown.

"Some people just weren't listening to our announcements, and we weren't making the announcements frequent enough at first," Johnson said.

Passengers traveling between Richmond and Fremont must now transfer at the Bayfair station to complete the trip. Before the fire, riders could take a train directly between Richmond and Fremont. The required transfer — which affects most but not all trains between Richmond and Fremont — will last until repairs are complete in six to eight weeks.

Because BART is usually so reliable, riders are unaccustomed to being forced to make changes, Johnson said.

Meanwhile, workers in BART's safety department continue to investigate the electrical fires. The first fire broke out at 4:26 a.m. as crews were upgrading some computerized equipment at the power substation. No one was injured.

BART must pay for the first $1 million in fire damage, but an insurance policy will cover the other millions of dollars of damage, Johnson said. Officials still did not know the full cost of the damage. BART may have to cut back temporarily on seat, carpet cleaning and other nonessential work until it restores operation of the Hayward car year that handles maintenance and cleaning, Johnson said.

Reach Denis Cuff at 925-943-8267 or dcuff@bayareanewsgroup.com.