Parcel firm Hermes has halted work at a depot in eastern Germany after two male workers died within hours of each other and a third was taken ill.
One of the men died at the depot, the other in a despatch van.
The deaths are being treated as unexplained and police for the moment are treating the circumstances as an unfortunate series of coincidences.
Police tested a poisonous substance found in a parcel but said the amount was not sufficient to cause death.
A 58-year-old man collapsed and died in the early hours of Tuesday morning, at the Hermes despatch depot in Haldensleben north-west of Magdeburg.
Hours later, at around 16:00 (14:00 GMT) on Tuesday, another worker aged 45 was found dead in the driver’s seat of a Hermes transport van.
Another man suddenly became ill on the site of the depot on Tuesday morning although police described that as a “completely normal medical emergency” and said he had suffered earlier health problems.
The Hermes depot employs 3,000 staff and the company temporarily halted operations on Tuesday night as a precaution.
A 120-strong team from the fire brigade were brought in to investigate the deaths and they inspected the van for possible toxic contamination.
As they opened the packages inside the van, small amounts of a toxic substance were found but police said the quantity discovered was not dangerous.
Post mortem examinations are being carried out on the two men, but police say initial medical reports suggest the two deaths are not linked and there are no specific signs of poisoning.
A criminal case will continue along with an investigation into hazardous substances, police say.
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