21.   Doctors were awaiting the results of tests to determine the nature of the tumors.

22.   Federal investigators were trying to determine the nature of the explosive for clues to suspects, police spokesman Michael Klein said.

23.   Health officials have not yet determined the nature of the infection, but Onishenko said previously that the disease was most likely a form of hemorrhagic fever.

24.   Investigators also collected stool samples from sickened individuals to determine the nature of the disorder.

25.   Military experts were called to determine the nature of the cargo.

26.   Officials said a similar scenario was likely this time, although they first need to determine the nature of the problem before they turn the main computer back on.

27.   Police were still trying to determine the nature of the explosive.

28.   They continued on with their mission to install the solar panel, while ground controllers tried to determine the nature of the mystery substance.

29.   They were sent to the Australian Government Analytical Laboratory, who reported there could be delays in determining the nature of the substance.

30.   Forensic scientists sifted through debris on the train in an attempt to determine the nature of the explosive used in the hope it could provide a lead.