“Following a meeting with the team owners and considering the health and well being of all participants is paramount, the Pakistan Cricket Board has decided to postpone the Pakistan Super League 6 with immediate effect," the PCB said.
The decision comes after the number of confirmed cases within the PSL bio-secure bubble rose from three on Wednesday to seven on Thursday.
The PCB "will focus on the safe and secure passage of all participants, and arrange repeat PCR tests, vaccines and isolation facilities to the six participating sides", it added.
Lahore Qalandars CEO Atif Rana said the decision was long overdue and that the PCB should have delayed the start of the tournament given the ongoing pandemic.
"Unfortunately, PCB said we should continue with the plan and other franchises supported the idea," he said.
The news comes just hours after PCB chief executive Wasim Khan had told reporters that all those within the bio-secure environment - around 300 players and support staff - had been offered Covid-19 vaccines.
PCB said it had secured a small allocation of the vaccine after highlighting the national team's international commitments and the reputation of the popular PSL Twenty20 tournament during talks with federal and provincial governments.
"While we live in these challenging times, the vaccine has been sourced to provide an added level of protection and comfort for players and all personnel inside the [biosecure] bubble," Wasim said, adding that the players and officials were "under no obligation" to have the vaccine.
The PCB did not reveal the names of all the new cases on Thursday. On Monday it was revealed Australian leg-spinner Fawad Ahmed had tested positive, forcing the rescheduling of Islamabad United's match with Quetta Gladiators by 24 hours.
On Wednesday England batsman Tom Banton tested positive for Covid along with a Karachi Kings staff member. On Thursday Pakistan allrounder Mohammad Faizan, who represents Lahore Qalandars, was also named as one of the players to contract Covid.
Australian allrounder Daniel Christian withdrew from the competition over fears of catching the virus and planned to fly out on Thursday.
It is not the first time the PSL has fallen victim to the coronavirus pandemic. Last year's competition was halted at the semi-final stages in March due to the number of rising cases in Pakistan. The games were rescheduled to November and held behind closed doors, when Karachi Kings won the title.
Karachi lead the current PSL table with six points from five matches.