CNN  — 

A crucial Puerto Rico power plant damaged in this week’s earthquakes could be out of operation for more than a year, the head of the island’s electricity authority told CBS News.

Power has been restored to about 50% of customers after a series of earthquakes since December 28, an official with the utility said Thursday.

With three major power plants expected to return to service between Thursday and Saturday, Puerto Rico Electric Energy Authority CEO Jose Ortiz said the entire US territory – with about 3 million residents – could have power by the weekend. A fourth could begin operating by Sunday, he said.

“The target is for Saturday to have everybody with power,” Ortiz told CNN.

But the Costa Sur Power Plant in Guayanilla suffered extensive damage in this week’s quakes. And the facility, which provides about a quarter of the island’s power, “will be out for probably over a year,” Ortiz said in an interview that aired on “CBS This Morning.”

Damage from this week's earthquakes was reported on the Costa Sur power plant.

Another complicating factor is the fact the plant’s equipment is decades old, Ortiz said.

“To be honest, those plants have over 60 years, basically,” he said. “Imagine you have a taxi, 60 years old, and you are required to run that 24/7.”

The plant’s operations manager, Angel Perez, appeared to differ on the timeline in a separate interview with CBS, saying it would be “no less than a month.” He said they would work “24 hours around the clock” to get the plant back up and running.

Officials are expected to hold a news conference to provide an update on their efforts to restore power.

Hundreds of tremors have struck Puerto Rico since December 28, with Tuesday’s 6.4 magnitude quake being the strongest and likely the most damaging. The quake, centered off the southern coast, left one man dead and caused dozens of homes and structures to crumble.