The Covid-19 outbreak in Karachi within the biosecure bubble during the Pakistan Super League (PSL) has prompted the PCB to look at contingencies. The league management is believed to be considering the option of playing the remainder of the tournament in Karachi instead of moving for the final leg to Lahore as scheduled, from March 10. The discussions are only in very preliminary stages - "food for thought" as one official said - but the Lahore Qalandars have already objected to the idea, insisting that fans in Lahore cannot be deprived of the matches and moving from one bubble to another won't increase the risk.

The PSL was meant to be played at four venues this year but due to the ongoing pandemic, the PCB decided to hold all 34 matches in Karachi and Lahore. The first leg of 20 matches is being played at the National Stadium in Karachi until March 7 and the following 10 league games and four playoff matches are scheduled for Lahore's Gaddafi Stadium. Chartered flights were meant to be used for travel between the two cities.

However, three overseas players - Fawad Ahmed, Tom Banton (who revealed his positive test publicly on Wednesday) and another Islamabad United player - and one support staff member with the Karachi Kings (Kamran Khan) testing positive for Covid-19 have led to concerns. The PCB spoke with all six franchises on Tuesday to remind them of the standard protocols required to maintain the biosecure bubbles.

As well as the positive cases, there were breaches of the bubble reported earlier that involved Peshawar Zalmi's Wahab Riaz and Daren Sammy meeting their franchise owner, who was not part of the bubble. There are believed to be other breaches as well, though the PCB insists that the "bubble isn't weak and there is no loophole".

The PCB is committed to making sure the league is completed successfully and safely with the final scheduled for March 22, but it is now mulling the best way of doing that. The board internally agreed that the schedule will not be tinkered with as long as a team has up to five affected players, since all teams have 18-member squads. But they are also working on a back-up plan ahead of the next round of PCR tests set for Thursday, which is considered the most crucial one after the recent outbreak.

All the franchise players and officials in the bubbles were initially being tested on a weekly basis but on Monday the PCB decided to carry out the PCR tests once every four days.

"It (keeping the entire event in Karachi) will give a wrong message by not continuing with the original plan," a Qalandars spokesman told ESPNcricinfo. "There was a lapse in the management either at a hotel or elsewhere but the risk involved is the same everywhere. It's about the management not about the venue so if the cases are positive in Karachi then you can't deprive the Lahore crowd of cricket they have been waiting for. It's in fact an opportunity for the PCB to show their ability to carry out their operation without panicking.

"Lahore has been a great host in the past and had successfully completed the South Africa series without any glitch. So we don't support any such plan which eventually gives out a message that we cannot control the situation. We are still going to travel through buses like every day here (in Karachi) as usual for the games and the only difference will be the one time traveling from Karachi to Lahore - that is on the chartered plane - which is fully sanitised. So it's beyond understanding how this is going to mitigate the risk and how you will be Covid-protected."

All players and officials - as well as families traveling with some of them - are part of a biosecure bubble in one hotel in Karachi. Each franchise nominated its own list of officials apart from the players to be part of the bubble, and everyone had to go through a three-day isolation period and return two negative tests before entering that bubble.

Two other franchises in the league questioned how exactly playing all the games in Karachi is going to reduce the risk as the teams are to move from one bubble to another, although one of them is open to a change of venue "if required".

The Karachi Kings owner Salman Iqbal supported the idea of staying back in Karachi. "I think we should keep the boys in the bubble and not make them travel. Flights, airports, new hotel, new procedures…I believe the players also don't feel comfortable leaving the bio-bubble. It is very important for Pakistan cricket and one wrong move could jeopardise the whole PSL and lead to loss of revenue. So I believe we should stay put."

Umar Farooq is ESPNcricinfo's Pakistan correspondent