DETROIT (AP) — Sections of downtown Detroit remain without power after high demand during this week’s 90-degree heat caused parts of the city’s aging municipal power system to fail.

The spotty outages that continued Friday morning affected traffic signals, 10 public schools and a handful of public buildings in and around downtown, including city hall. Wayne State University also lost power Thursday after three of five lines supplying the municipal system went down over two days.

City officials estimated Thursday that power could be restored by Friday afternoon. A message seeking updates was sent by The Associated Press early Friday to a mayor’s spokeswoman.

Early Friday, temperatures were in the 50s after topping 90 degrees Tuesday and Wednesday.

The municipal system serves public buildings, so the outage didn’t affect most power customers.

Copyright 2011 The Associated Press