It happened at about 1:30 a.m. on Wilmington Drive near Chiswell Drive in Melville.
The limo was returning from a wedding with five people inside when it was struck by a Mercedes sedan that crossed over a double yellow line, authorities said.
Police say the driver of the Mercedes took off from the scene and was picked up by another vehicle, a dark-colored sedan.
The driver and all five passengers in the limo were taken to a local hospital. One of them is in serious condition.
The search continues for the driver of the Mercedes.
Detectives are asking anyone with information about the crash to contact the Second Squad at 631-854-8252 or anonymously to Crime Stoppers at 1-800-220-TIPS.
----------
* More Long Island news
* Send us a news tip
* Download the abc7NY app for breaking news alerts