About 200 customers in downtown Sioux Falls are still waiting for power after an electricity system caught fire beneath Phillips Avenue.

Xcel Energy says the outage, which happened at 4:37 a.m. Friday knocked out power to more than 500 customers.  Power crews were able to restore power to about 300 of them within about an hour.

Sioux Falls Fire Rescue was called to 9th Street and Phillips Avenue when flames and smoke blew manhole covers out of the street.  A sidewalk also buckled.

The area still without power covers nine square blocks between 8th Street and 11th Street and from Phillips Avenue to Minnesota Avenue.  The incident is the worst Xcel experts have seen in the downtown area in more than 20 years.

Xcel says all of the underground electrical equipment in that area needs to be replaced and they don't know how long that could take. The company is bringing in crews from the Minneapolis area to also help with repairs and restore power.  They won't know how long that could take but power will be out into Saturday, possibly Sunday.

They do not know what caused the fire.  That is under investigation.

We'll continue to keep you updated on the progress on KELOLAND News and KELOLAND.com.  You can watch the Special Report by clicking on the video player below.