A disgusting, bloody pig head on a spike was left in front of an L.A. police station … now cops are trying to find out who left it.

Law enforcement sources tell TMZ … the swine skull was discovered outside the LAPD’s infamous Rampart station Saturday afternoon, and though the message is hardly subtle … it’s unclear if the gesture was intended as a serious threat.

We’re told the department’s looking into it further and reviewing surveillance footage in the area. Cops are also being advised to maintain a low profile right now while off-duty … in order to avoid confrontations with a public that’s heated about police practices. Cops are well aware that’s why hundreds of thousands, in L.A. alone, have been marching.

As you know … there have been several incidents of violence involving cops the past 2 weeks during the unrest over George Floyd‘s death, systemic racism and police brutality in the U.S.

Some of the more alarming incidents include a Chicago cop charging and punching a guy, cops in Buffalo pushing an elderly man to the ground and a vehicle running over an NYPD officer.

It’s worth noting … LAPD’s Rampart Division made national headlines for a massive police corruption scandal in the late ’90s with officers implicated in police brutality, drug deals and even bank robberies.