The time is now 5pm, and according to the well-informed SPUG forum, the "North South MRT line is now suspended." This news is still not out in official channels, it seems (not on their sites anyway).
According to the poster's friend, "Someone jumped off the platform at Bukit Batok MRT station. I was there right after it happended though thankfully I didn't see any sights of the accident."
The info was posted on the forum at 2.50pm.
Another forum poster said that he wasn't in the train, but was told to leave the station whilst waiting for the train in the other direction. He said that he didn't see the guy jump, but the police and the SCDF arrived minutes after the station was closed.
We shall keep our ears open for more official reports.