The Counter Terrorism Department (CTD) investigative teams visited New Town Rawalpindi and Sector I-10/4 Islamabad on Sunday and obtained data of stores to identify the accused involved in sending the arsenic letters to high ups.
According to the 24NewsHD TV channel, the investigative teams also questioned the owners of the stores where arsenic power was reported to be available.
The three investigative teams were probing the letters laced with poisonous substances which were sent to the judges of Supreme Court and High Courts and Punjab Chief Minister Maryam Nawaz Sharif. Arsenic powder has also been found on these letters.
The investigation teams obtained the data of stores located near both the areas where arsenic powder was likely to be obtained.
The investigation teams have directed shopkeepers to keep record of buyer's information before purchasing any suspicious chemical.
However, during the investigation no arrests were made so far from Islamabad and Rawalpindi.
Earlier, authorities have put post offices and courier companies on alert. The post office officials and courier services have been asked to be vigilant and check thoroughly any letter sent to any high-profile personality.
Sources said that all the post offices and courier services were directed not to open any 'suspicious' letter addressed to high-profile personalities.
Reporter: Farzana Siddique