LONDON (CNN) -- British field hockey authorities have been forced to apologize "unreservedly" to South Africa after an old national anthem from the days of apartheid was played before an international game this week.

Great Britain Hockey called the mistake "sensitive" and "unfortunate."

"It was completely shocking," the chief executive of South Africa hockey said of hearing the pre-1994 anthem "Die Stem" being played before Tuesday's game in London.

"I thought, 'What is that?' And when I listened further, I realized it was 'Die Stem.' I couldn't believe my ears," Marissa Langeni said Thursday.

Some of the younger players on the team didn't even know what song was being played, she said.

The anthem dates from the days of white minority rule over South Africa and was replaced when Nelson Mandela became president in 1994.

"For the majority of South Africans, we don't relate to that anthem," Langeni said. "It was the anthem of a small section of our community. It's as good as not having played an anthem."

"If they flew the old flag of the country, I would be equally surprised," she said.

Tournament organizer Great Britain Hockey on Wednesday published "a full and unreserved apology to the South African women's hockey team and their supporters for mistakenly playing the wrong national anthem before South Africa's match with Great Britain."

GBH Chief Operating Officer Sally Munday blamed the mistake on "a contractor responsible for sports presentation at the event."

She said organizers had not checked the anthem in advance and took full responsibility for the mistake.

Langeni said she was very satisfied with the apology, calling the error "a bit of an administrative blunder."

South Africa beat Great Britain 3-1, an upset for the visitors.