A "huge release of energy" that shot a manhole cover into the air caused traffic delays near 17th Avenue S.W. and initially knocked power out for thousands of customers Wednesday evening, Enmax told CBC News.

Calgary police received calls about the incident just before 5 p.m.

Traffic on 21st Street S.W. near 17th Avenue was closed following the explosion, which Enmax says was possibly caused by build up from a nearby cable failure.

Initially 3,800 customers in the area were without power, but that was down to about 125 by 6 p.m.

No injuries have been reported.