What was found
WHILE TURNING ON LT AND RT LANDING LIGHTS AND NOSE LIGHT NOTICED SPARKS FROM LIGHT SWITCHES. UNABLE TO DETERMINE WHICH SWITCH ACTUALLY SPARKED. WHILE CHECKING PROBLEM, FOUND NOSE GEAR TAXI LIGHT TOGGLE LOOSE FROM SWITCH, BUT FOUND NOTHING ELSE OBVIOUS WRONG WITH SWITCHES. TRIED SEVERAL TIMES, BOTH INDIVIDUALLY AND TOGETHER, TO DUPLICATE PROBLEM BUT COULD NOT. ACFT OK TO CONTINUE SERVICE.