Tens of thousands of homes in Berlin will be without electricity until Thursday as authorities struggle to repair power cables seriously damaged in a suspected arson attack, officials have said.

Some households may also be without heating as the outage has affected local systems at a time when the German capital is blanketed in snow and temperatures are hovering around freezing.

Emergency services were alerted early on Saturday that several high-voltage cables on a bridge near a power plant had gone up in flames.

Firefighters quickly extinguished the blaze, but about 45,500 homes and 2,200 businesses in districts in south-west Berlin were left without power, according to the grid operator Stromnetz Berlin.

A pedestrian walks through the Lichterfelde district in western Berlin after a major power outage. Photograph: Filip Singer/EPA

The extensive damage means that about 35,000 households will be without electricity until Thursday afternoon, Berlin authorities said in a statement. Power should be restored to other homes by early Sunday.

“We are dealing with a particularly serious power outage affecting tens of thousands of households and businesses, including care facilities, hospitals, numerous social institutions and companies,” said Franziska Giffey, Berlin’s senator for economic affairs.

The local district heating system, which transports heat around a pipe network in the area, is affected as it is powered by electricity.

Stromnetz Berlin warned that repair work would “take a very long time”, with media reports saying that cold weather was hindering efforts to lay new underground cables.

Police deployed about 160 officers to the site of the incident in the Lichterfelde area and said they were “investigating on suspicion of arson”.

They drove vans equipped with loudspeakers through the affected areas, urging residents to stay with friends or relatives elsewhere if possible, use mobile phones sparingly and ensure they had torches to hand.

Local train stations were affected, with electronic information signs and ticket machines not working – although the trains were still running.

Giffey said Saturday’s outage was worse than one in September, when tens of thousands were also left without power in Berlin after a fire hit electricity pylons. Police also suspected arson in that case, and an unnamed anarchist group claimed responsibility online for starting the blaze.

Germany has been on high alert for sabotage activities directed at its infrastructure, including from foreign actors such as Russia.