While admitting the results had been "encouraging", Mr Shields said that pre-empting the outcome of the further analysis would be wrong at this stage of the inquiry.
He said: "We have results from toxicology now but they will require further investigation and analysis, therefore it would be totally inappropriate for me to elaborate any further than that at this time."
Woolmer died on March 18th, the day after Pakistan lost to Ireland at the World Cup, and initial police reports suggested that he had been strangled.
However, the lack of bruising or signs of a struggle then led police to believe that Woolmer may also have been drugged.
The results of the toxicology reports would provide the key to this information but Mr Shields wants to be sure of the accuracy of the report before releasing the information it contains.
He did reveal that two of the four Scotland Yard detectives who are assisting investigations had returned back to the UK but said that this was standard procedure at this stage of the inquiry.
Mr Shields also said that ongoing analysis of CCTV footage from Woolmer's hotel was helping police track the comings and goings on the 12th floor where his room was situated.
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