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Shooting outside nightclub in Tempe, Ariz. wounds 13

Updated at 10:40 a.m. ET: TEMPE, Ariz. -- An altercation outside a nightclub in suburban Phoenix erupted in a shooting, leaving 13 people wounded including two in serious condition, police said Saturday.

Police are looking for two young men as possible suspects, who fled after the gunfire around midnight Friday in the parking lot of The Clubhouse Music Venue.

Tempe Sgt. Steve Carbajal confirmed to msnbc.com that at least two of the injured were taken to local hospitals and were in serious condition, while the others were treated for wounds that appeared to be less severe.

In an emailed statement, Carbajal said the incident occurred at 11:30 p.m. local time (2:30 a.m. ET).

Police are hunting the pair, described as black men wearing dark clothing, who fled on foot from the club on East Broadway Road, located about 7 miles east of downtown Phoenix.

Carbajal described the shooting as the result of "some sort of altercation" at the club, where a rap music concert was going on.

He didn't have immediate details on the altercation, if both of the men are suspected of firing weapons, and on the type of guns used. It's unclear whether the shooting occurred inside or outside the club.

He said some of the injured drove themselves to the various hospitals in the area so police aren't sure if there were other victims besides the 13. Their identities have not been released.

Four hours after the shooting, the parking lot was virtually empty with only police activity apparent. All entrances to the club's parking lot were cordoned off with tape and squad cars were posted around the area. Detectives are investigating what led up to the shooting and are working on identifying suspects, reported abc15.com.

The website for the club - located in a strip mall within two miles of Arizona State University's main campus in Tempe - says it has been in operation for six years hosting music shows for all age groups nightly.

Calls to the club went unanswered early Saturday.

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Msnbc.com staff and The Associated Press contributed to this report.