Police have said they have found no evidence that an explosion occurred in Londonderry on Tuesday evening.
The PSNI logged a multitude of calls from people on both side of the River Foyle and from as far away as Eglinton and Drumahoe, on the suburbs of the city, about an explosion, but no obvious source has been found.
Theories and rumours flew around the city with reports of exploding tyres, masked men and a possible attack on police.
Social networking sites Facebook and Twitter lit up with speculation a HGV on John Street on the city side, which blew two tyres shattering windows, was the cause, while others said it was a gas cylinder, and more again insisted that masked men spotted near Dunfield Terrace in the Waterside had mounted an attack on a police patrol in the area.
As daylight broke on Wednesday and police carried out extensive searches of Spencer Road and its surrounding streets in the Waterside, residents who had been evacuated from their homes on Tuesday night waited for the cause of the loud bang to be revealed - but they were to be denied an explanation.
People living on Spencer Road and its surrounding areas were allowed to return to their homes on Wednesday afternoon as police removed all cordons except those around the Quarry Steps. This area was searched yesterday using specialist equipment, but still there were no answers to the mystery.
Police have now said that unless further information comes to their attention the matter will remain a mystery.
As the operation wound up yesterday a police spokeswoman said: "An extensive specialist search has been carried out and we have found no indication or evidence of an explosion in that area.
"From approximately 5pm on Tuesday police received a number of telephone calls in relation to this incident.
"We do know that a lorry sustained two tyre blow-outs on John Street around the time of the initial reports - this resulted in some damage to windows in the immediate vicinity of the vehicle.
"Many people we spoke to reported a bomb explosion, one caller stated that debris had fallen on the building of a local business, and others said that their windows and houses shook.
"Police also had to take into account a report of masked men on Dunfield Terrace.
"As a result of all those calls the decision was made to focus our searches and inquiries in the Spencer Road area.
"We appreciate that this incident has caused disruption to residents and local businesses, however we feel that we took the necessary steps to thoroughly investigate the reports and keep the public safe.
"The cause of the reported explosion remains unclear. Unless further information comes to light police have currently exhausted all available lines of inquiry."
However, the search of the Quarry Steps was not entirely fruitless, as a small amount of suspected herbal cannabis was found with an approximate street value of between £400 and £500.