An American woman has been mauled to death by a lion that leaped through an open car window at a game park in South Africa, an official has said.

A man who was driving the car was reportedly injured when he tried to fight off the lion. The tourists have not been named.

The police have launched an investigation into the incident, which was witnessed by other visitors to the park.

Scott Simpson, assistant operations manager of the Lion Park, which is outside Johannesburg, said: “We had a gentleman and a lady driving with the windows wide open. The lion came through the passenger side window and attacked her. The man sustained slight injuries trying to fight her off.”

Speaking to the eNews Channel Africa (eNCA), he said: “Our staff working at the top of the camp tried to get the lion away from the car. Ambulances were called immediately but it was too late.”

Visitors to the park are given numerous warnings not to leave their windows open, Simpson said. “We make it so clear. We put signage up everywhere that people must keep their windows closed. We hand them a slip of paper when they enter the park; I really don’t understand why people think its OK to leave windows open.

“We’ll of course have an internal investigation of our own to find out exactly what happened. We’ve got statements from the witnesses that were there at the time. We’ll also of course take written statements from our staff and put together a report, and hopefully we’ll get some findings from that.”

The attraction was opened by the Chipperfield Circus in 1966 and is described as a mix of zoo and game reserve with “super close-up animal views guaranteed”. Visitors can board buses with protective grills and tour guides, or drive their own vehicles through spacious enclosures where lions roam freely. Adults and children are commonly seen petting lion cubs in managed pens.

Celebrity visitors have included singers Shakira and John Legend, Brazilian footballer Kaká and actor Natalie Portman. The Lion Park was voted one of the top 100 tourist destinations in the world by Newsweek magazine in 2013.

Simpson told eNCA: “We’ve not had a fatality like this before so it’s hard to say how this will go, but in terms of business I don’t think people will stay away. I think people realise that if they come here and follow the rules and actually do what they’re told and follow the signs, then it is a safe place to be.

“So I don’t think people will stop coming, I don’t think it will harm us in that way, but of course we don’t want these incidents happening again, and our condolences to this family.”

The lion, a female, has been taken to a separate enclosure until the park’s investigations are complete. There are no plans to put it down.

This is the third attack at the park in the past four months, according to eNCA. An Australian man was bitten by a lion in March after he left his window open and later posted images of the incident on Facebook. A 13-year-old who cut through the park while riding his bike was attacked by a cheetah a few days later.