Germany has opened a counterterrorism investigation after an explosive-laden drone was found near a runway at Leipzig/Halle airport, prompting the closure of parts of one of Europe's biggest cargo hubs.Investigators were also examining what a DHL cargo plane had struck in the air after being diverted from the airport in eastern Germany during the disruption.Airport workers discovered the drone in a restricted cargo area near the southern runway overnight on Wednesday, local time A source familiar with the incident said the plane belonged to DHL.The southern runway of the airport, a major hub for DHL and Ukraine's Antonov Airlines, remained closed while explosives experts examined the drone and removed its detonator, according to authorities.Interior Minister Alexander Dobrindt had scheduled an emergency meeting with the heads of Germany's security services for Wednesday night.German airports are on high alert after a series of unauthorised drone overflights at sites including military facilities, energy terminals, seaports and logistics companies.Federal police have said the overflights could have been organised by Russian agents.Germany's Bild newspaper reported that the Leipzig drone had been found lying in the immediate vicinity of a Ukrainian Antonov cargo plane