A Puerto Rico Electric and Power Authority brigade work in a remote off-road location to repair a downed power transmission line in Ponce, Puerto Rico on November 29, 2017. / AFP PHOTO / Ricardo ARDUENGO / TO GO WITH AFP STORY By Leila MACOR, US-PuertoRico-power-weather-reconstruction-hurricane        (Photo credit should read RICARDO ARDUENGO/AFP/Getty Images)
A Puerto Rico Electric and Power Authority brigade work in a remote off-road location to repair a downed power transmission line in Ponce, Puerto Rico on November 29, 2017. / AFP PHOTO / Ricardo ARDUENGO / TO GO WITH AFP STORY By Leila MACOR, US-PuertoRico-power-weather-reconstruction-hurricane (Photo credit should read RICARDO ARDUENGO/AFP/Getty Images)
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(CNN) —  

In another blow to its recovery efforts, an island-wide power outage left most of Puerto Rico in the dark, with only a fraction of residents regaining electricity by Wednesday night.

The latest blackout prompted Gov. Ricardo Rossello to call on the Puerto Rico Electric Power Authority (PREPA) to cancel its contract with the subcontractor that caused the massive outage.

“I have suggested to the PREPA Board of Directors that they cancel the contract with the Cobra subcontractor who is directly responsible for this power outage,” he said in a statement Wednesday.

An excavator operated by D. Grimm, a subcontractor for Cobra Acquisitions, apparently caused the blackout, according to the authority. Workers had been removing a fallen tower when the machine got too close to an energized line and an electrical ground fault caused the outage, according to Mammoth Energy, Cobra’s parent company.

The same company was responsible for an outage that affected 870,000 customers after a tree fell on a power line last week, PREPA said.

“This is the second power failure that has affected the people of Puerto Rico in less than a week,” Rossello said. “This incident denotes the need to transform PREPA into a cutting-edge, modern and robust corporation. This is another example of why Puerto Rico’s energy infrastructure needs to incorporate new forms of power.”

As of 8 p.m. Wednesday, only 334,000 customers in the US commonwealth had electricity again, according to a tweet from PREPA. It also said via Twitter that it’s working to restore service through the island.

The game must go on

Hours into the blackout, the lights came on at the Hiram Bithorn Stadium in San Juan for a baseball game between the Minnesota Twins and Cleveland Indians. The Wednesday game lasted 16 innings before a sold-out crowd of 19,537, according to MLB.com.

Backup systems and mobile tower lights allowed the game to go on as planned, said San Juan Mayor Carmen Yulin Cruz.

“Playball! Nothing will stop us,” she tweeted.

Many watched the game then went to homes without electricity.

Power was to be restored to customers who had electricity before the latest outage within 24 to 36 hours, according to PREPA.

Most of the island had had its power restored as Puerto Rico began the process of rebuilding its decimated electrical grid after Hurricane Maria struck in September and knocked out power to nearly 1.4 million customers.

“Seven months after Maria, we are back where Maria left us,” Cynthia Garcia Coll, a professor at Carlos Albizu University in San Juan, said via email.

Hospitals first

Cruz worried that the latest outage signaled that Puerto Rico won’t be prepared for the upcoming hurricane season.

“Our electrical system is weak, at best,” the mayor said Wednesday. “Today’s blackout makes it painfully obvious that we are not yet ready for the coming hurricane season, which is only 43 days away.”

The Atlantic hurricane season lasts from June through November. This season could be a slightly above average one, according to a preliminary forecast.

“Today’s total power outage in Puerto Rico pinpoints the fact that we are still in a very fragile state,” she said. “Moreover, the suffering of the Puerto Rican people seems to be nowhere nearing an end.”

Since the monster storm slammed into Caribbean territory in September more than 3.4 billion hours of electricity have been lost there, according to a recent report.

Puerto Rico’s power outage is now the second-largest blackout in history

It’s the largest blackout in US history (in terms of customer hours) and the second largest in the world – after the outage caused when Typhoon Haiyan tore through the Philippines in 2013, killing more than 6,000 people.

CNN’s Ray Sanchez, Leyla Santiago, Nicole Chavez, Natalie Gallón and Keith Allen contributed to this report.