Police investigating the stabbing murder and torching of Long Island beauty Rebecca Koster yesterday took a possible suspect into custody, grilled him and then released him — but searched his home and removed possible evidence, a law enforcement source told The Post.

The Post has been asked not to name the possible suspect or reveal his address.

The Post yesterday saw Suffolk County investigators remove a small box and three large bags, along with weight-lifting weights and a broom and dustpan from the unnamed man’s Long Island home.

The person taken in for questioning was not the victim’s boyfriend, Dan Mayor, 28, The Post has learned.

Mayor was the last person to see Koster, 24, of Medford, before she vanished Dec. 4. Her body was found dumped in a Connecticut field that evening.