The 24-year-old jetski driver, who is accused of causing the deaths of two women in the accident, will now remain in custody until July 28th.
The custodial period was extended by Copenhagen City Court last week, reports news agency Ritzau.
The man was arrested after the May 6th tragedy and originally remanded in custody for four weeks.
“His custodial period has been extended by four weeks,” senior prosecutor Elisabeth Boserup of Copenhagen Police's special law department told Ritzau Tuesday.
Leah Bell, 18, and Linsey Malia, 21, who were both United States nationals, were killed when the man's jetski collided with their boat near the Langebro bridge in Copenhagen Harbour.
The 24-year-old man has been charged with double manslaughter, recklessly endangering lives and leaving the scene of an accident.
Seven other people who were also riding jetskis in the harbour at the time of the accident were also charged with putting others in danger by riding the jetskis at excessively high speeds.
All eight attended preliminary hearings at Copenhagen City Court Sunday on May 7th.
The group were reported to have ridden their jetskis at speeds of up to 90 kilometres per hour.
This was denied by the jetski riders themselves, although one did estimate that they travelled at up to 50 kilometres per hour.
All eight jetski riders sailed to the harbour in nearby Brøndby after the accident, where they handed themselves in to police.
The use of jetskis, waterskiing, and windsurfing are all prohibited in Copenhagen harbour, and Denmark forbids sailing on jetskis within 300 metres from the coast as well as in national park areas.
Within this distance the maximum speed is designated as five knots – approximately 9 kilometres per hour.
Last month, Denmark's justice minister Søren Pape Poulsen and Copenhagen mayor Frank Jensen both stated their intentions to introduce stricter measures on jetski use.
The 24-year-old jetski driver was initially detained partly due to previous convictions for violent behaviour and theft, reported broadcaster DR, which was present at the preliminary hearing.
He will now remain in custody after the court reviewed his detainment, as is required every four weeks under Danish law.
The 24-year-old's defence counsel, Jane Ranum, told Ritzau Tuesday that she did not expect the extended detainment of the man to be appealed.