James Wehr and Lexi Kramer‘s social media pages are under a microscope as cops investigate whether he was boozing the night they died in his McLaren … TMZ has learned.

The Irvine Police Department tells TMZ … “We are conducting an extensive investigation that looks at every possible aspect that contributed to this collision,” and that includes reviewing images James and Lexi posted last Sunday while out on a date.

We’re told cops are trying to figure out if James was drinking before he got behind the wheel that night … so, they’re keenly interested in toxicology testing results from the Medical Examiner’s Office.

In the meantime, they’re reviewing social media for any clues about where they went, and what they did, in the hours leading up to the crash.

One of Lexi’s family members tells TMZ … her posts that day showed her going to breakfast with James, spending the day together and, later, dinner at Nobu and drinks at a swanky hotel.

Lexi’s family says James flew her out to California from Florida after meeting on the internet … and this was their first in-person meeting. He was married, but Lexi’s family says he’d told her he was getting divorced.

The family member tells us Lexi said she and James “finished each other’s sentences” and had a “deep connection she hasn’t experienced before.”

As we previously reported … Wehr was behind the wheel of his 2019 McLaren sports car early Sunday morning, when he lost control and plowed into a tree. Police believe speed was a factor in the crash.

In video TMZ obtained, you see Wehr drive over a wet patch of road, and seconds later, he skids off the road … his car exploding on impact with the tree.

Wehr’s family has hired a lawyer who’s suggesting they might file a lawsuit against Irvine and/or McLaren.