Lakers forward Pau Gasol's hamstring injury may be more serious than initially believed.

He underwent a sonogram that revealed he may have a slight tear in his right hamstring. Gasol underwent a more detailed MRI on Monday, but the results aren't yet known.

"It's not as sophisticated a test," Lakers spokesman John Black told the Los Angeles Times about the sonogram. "That's why we are doing the MRI. It's much more sophisticated."

Gasol has been shut down for three weeks now.