"we don't know yet" is a valid response and gives the rest something to work, and it shouldn't annoy you that it's being asked, first of all because if they are asking is because you are already late.

you have to to tell the rest of the team what you know and you don't know, and update them accordingly.

until your team says something the rest don't know if it's a 30 minute thing or the end of the world or if we need to start dusting off the faxes.