Germany's antitrust watchdog said it started a more detailed probe into the planned takeover of DSM's Elastomers unit by Lanxess, the world's largest synthetic-rubber company. "We want to assess the effects on the competitive environment more closely," a spokesman for the German Federal Cartel Office told Reuters on Friday. Lanxess said in December it had struck an agreement with DSM to buy the unit, which markets a type of synthetic rubber branded as Keltan, for €310 million ($424.9 million).