At 9:17 p.m. on Saturday, thousands of residents of the Rhineland city of Cologne simultaneously reached into their chiming purses and pockets. Locals in neighboring Leverkusen would do the same 39 minutes later. It's fairly easy to guess that an app-based "catastrophe alarm" warning residents to seal their windows as a potentially toxic cloud of smoke formed over the Rhine wasn't the message anyone expected at going-out time on a Saturday night.

Residents of northern Cologne and riverside Leverkusen obliged as 175 firefighters worked on a blaze of unknown origin at Leverkusen's Chempark, a 480-hectare (1,200-acre) block of chimneys and labs on the right bank of the Rhine and just a couple of kilometers from downtown. By 4 a.m. and with no injuries, the fire was out and residents were told they were safe, that special vans had been dispatched to test the air and they'd found no abnormalities, they'd determined it breathable. The Rhine River reopened to shipping traffic on Sunday and children went back to school on Monday, and the Chempark, with the exception of the heavily damaged portions of the burned first floor of the six-level siloxane-and-solvent facilities, was back in business manufacturing and disposing of more than 5,000 chemicals. Firefighters reported that some of the water used to extinguish the blaze had flowed into the Rhine. They also warned locals to stay away from potentially toxic soot.

While the chemical processor tallies its losses, several local representatives are demanding answers. Leverkusen's Pirate Party, for example, wants to know what sort of evacuation plan the city has for scenarios such as Saturday's. And, perhaps more importantly, they are asking why it took an hour from the time the fire began for any warnings to be released and why Cologne's fire department warned people there 39 minutes before Leverkusen's alerted its residents.

'No extensive information'

Greens also plan to bring up questions with the mayor at a meeting next week. They want to know how sufficient public information will be ensured - and not just in future disaster-warning situations, but as officials examine the potential environmental consequences of the clear-for-now situation at the chemical plant.

"So far, we have no extensive information about the fire in Chempark," Marc Nohl, the chairman of Leverkusen's Greens, wrote in an email, in which he shared councilors' letter to the mayor. "Therefore, we can't currently give a serious position on this fire. For now, we are proceeding, nevertheless, on the assumption that the population and the environment were at no point endangered." He added that "for a final judgment, however, we have requested the mayor of the city of Leverkusen to give a report at the coming meeting of the environment committee."

Until that further information comes, locals, too, will have to proceed on the assumption that the clouds of smoke that billowed from the Chempark late Saturday have not done lasting damage to their air quality. The fire is out now, but, whatever the inquiries ultimately determine, their alarm was far from false.