For almost a week, Björklinge's 3,000 residents have had to fetch drinking water from tanks after contamination is discovered.
Samples showed too high levels of PAH, a group of hydrocarbons that can be carcinogenic with long-term intake.
Since then, Uppsala Vatten has tried to pinpoint the cause of the pollution.
- We take water samples in different places to see where there is a higher concentration of PAH.
Right now we have no forecast for how long it will take, says Bertil Lustig.
- We work according to some theories, but which I do not want to mention.
"Pressure in the pipes"
There is no indication that any pipe has broken, and that harmful substances have been leaked as a result.
- There is pressure in the pipes so nothing has broken.
And it is clean groundwater that enters the waterworks, and out it is also clean.
It is in the system after the waterworks that we look for a cause, says Bertil Lustig.
VMA is lifted
In connection with the associations being discovered, a VMA (important message to the public) was sent out to residents in Björklinge not to drink the water from the tap.
On Monday, the VMA will be lifted, but that does not mean that the water is drinkable.
- We believe that people have received the information now, then we no longer need a VMA, says Bertil Lustig.
Have you come up with anything at all in the last week?
- I think so, absolutely.
We have taken many samples that are analyzed to see where and what the cause is.
But I have no forecast for when it will be ready.