New Delhi, Feb 12 :Police sources on Sunday claimed to have detained one person in the double murder case in Old Delhi, wherein two trader brothers were found dead with their throats slit. A labourer, identified as Sonu, has been detained in connection with the murders of Devender and Rajkumar Manchanda, they said. Devender and Rajkumar were found murdered with their throats slit inside their office at Ram Bazar in Mori Gate on Saturday.The sources added that Sonu was missing along with another worker after the incident.