A bag of bodily waste was left at the back door of a People's Action Party branch office in Yew Tee on Monday, days after Chua Chu Kang GRC MP Alex Yam issued a stern warning to loan sharks and runners active in the constituency.

The office is located at Block 608 Chua Chu Kang Street 62.

In a Facebook post on Thursday evening, Mr Yam said: "Whether it was a coincidence, an act of mischief or otherwise, we will not stop in our efforts to keep our town safe for all residents."

He also shared that he had met with officers from Choa Chu Kang Neighbourhood Police Centre (NPC) who told him that one suspect has been arrested recently for loan shark activities. He added that the installation of police closed-circuit TV (CCTV) cameras has "progressively" been rolled out to various clusters of blocks. They comprise Blocks 527 to 533, 540 to 552A and 687 to 692A.

Last Saturday, Mr Yam said in another Facebook post that the authorities have brought forward the installation of CCTV cameras at Block 538, which had been targeted by loan sharks. He said that residents of the block had been receiving letters threatening that they would be locked in their flats. The CCTV cameras were installed at the block two weeks ago, a fortnight sooner than they were due to be put in.

In that post, Mr Yam also said: "You threaten my residents, means you threaten me and my 500 volunteers. I don't like threats and we certainly don't take them lying down."

Based on police recommendations, Mr Yam said on Thursday that residents who receive suspicious letters should bring them to the NPC, untouched in a clear plastic bag or re-sealable zipper bag, so that any residual DNA will not be tampered with.