"Well, initially it's gone up about 40 percent from 2007," said L.A. County Sheriff's Dept. Sgt. Leo Bauer.
Dan Finkelstein said thieves stole two of his bikes locked up at the Orange Line. He said the first one was stolen off the bike rack.
"The second time, I cabled it up to an area where there was much more light and visibility, and that one got stolen too," said Finkelstein.
So far this year, detectives say more than a dozen bikes have been stolen from routes along the Orange Line, where most of the thefts have occurred.
"Our detectives have gone ahead and conducted what's known as a 'bike sting operation' recently, and they've arrested three individuals for stealing bikes here on the Orange Line," said Sgt. Bauer.
Investigators said that with the dramatic increase in transit ridership, more people are riding bikes to Park-N-Rides and locking up. They say that's also brought out criminals looking for easy locks to pick.
"This type of chain lock can be easily defeated by just simple, heavy-duty wirecutters, or some small boltcutters," said Sgt. Bauer. "You can walk right up, snap the chain, and then take the bike and leave."
Authorities said criminals don't like heavy-duty "U-locks."
"Because it would take too long to cut through that type of lock to try to take the bicycle," said Sgt. Bauer.
Authorities said a sure way to protect your bike is to rent a bicycle locker -- most Metro stations have them at a cost of about $25 per year.
Or you can buy a bike that you can fold up and carry on or off the Metro.
"I use a folding bike," said Francisco Oaxaca, MTA. "And I take the bike with me wherever I go. More folding bikes are coming on to the market in all price ranges. So they can average from a couple hundred dollars, to a thousand or more. It just depends on how much you're willing to pay to get this type of bike and use it on the transit system."
Authorities say if your bike is stolen, it would help them solve the crime -- and maybe even get your bike back -- if you're able to provide them with the serial number, found on the bottom of the frame of the bike.