Facebook sales ending in armed robberies in Mass.

LOWELL, Mass. - Police in Lowell, Mass. are warning residents about a string of robberies at gunpoint that began with Facebook users posting items for sale online, reports CBS Boston.

Lowell police said they are investigating multiple armed robberies that took place in recent weeks in the city north of Boston.

In each case, police said the victim had advertised an item for sale via Facebook.

When the person selling the item met up with the purported buyer, the seller was robbed at gunpoint, according to police.

"Please exercise extreme caution if you decide to conduct such business," Lowell police said in a Facebook post.